The present invention relates to a device for opening slivers and, more particularly, to a device for opening slivers for feeding an OE spinning device comprising a sliver feed device defining a sliver clamping position and a rotating opening roller having a circumference with spirally extending combing elements for engaging at the clamping position into a sliver being fed by the sliver feed device.
For open-end (OE) spinning, a sliver is separated into its individual fibers by means of an opening roller carrying combing elements, e.g. sawteeth or needles, on its circumference. The sliver is uniformly fed to the opening roller by a feeding device. To this end, a known feeding device comprises a grooved, serrated or fluted roller and a feed table or a feed trough, both of which cooperate to form a clamping position. The sliver passes on the deflection edge of the feed table into the effective range of the combing elements on the circumference of the revolving opening roller. The sliver is deflected thereby and combed out as so-called fiber tufts. The opening roller is usually driven at a circumferential speed of 20 to 30 m/sec. In order to avoid an uneven opening of the sliver and an increased loosening out of fiber tufts which were not opened or opened only incompletely, high circumferential speeds of the opening roller are selected.
The combing elements are arranged on the circumference of the opening roller in such a manner that their tips, which ideally are equally spaced relative to the axis of rotation of the opening roller, are located on an imaginary spiral or helical curve, comparable to a single or multiple thread. The combing elements and their forward surfaces are usually inclined at an angle of 15.degree. to 20.degree. in the direction of travel of the opening roller to support the drawing in of the fibers into the channels formed by the spiral course of the tips between the combing elements. However, such a so-called positive breast angle of the combing elements makes it difficult to loosen the fibers from the opening roller for further transport in the air current. In order to gain support during the loosening of the fibers from the combing elements of the opening roller, the speed of the transport air is adjusted higher than the circumferential speed of the opening roller. The fibers are transported to a twist-imparting device such as a spinning rotor or friction rollers, where they are collected into a desired yarn thickness, drawn off and twisted.
An open-end spinning device with two friction rollers and designed as a friction spinning device is described, e.g., in German Patent Publication DE 195 26 845 A1.
German Patent Publication DE 24 40 224 B2 teaches blowing air radially to the opening roller in the area of the fiber tufts in order to press the fiber tuft onto the combing elements of the opening roller. This is intended to prevent the freely suspended fiber tuft from moving away from the fittings and the opening from becoming worse. However, it is very difficult to bring about a uniform dosing of the supply of air to all spinning locations. In addition, there is the disadvantage that the current of pressurized air entrains short fibers and that the additional, constant consumption of compressed air significantly increases the operating costs.
German Patent Publication DE 31 27 415 A1 discloses a sliver feeding and opening device which is intended to hold the sliver in the area of the fittings of the opening roller by using stationary support elements designed as a cogged strip and to prevent a shifting of the fiber tuft in the axial direction of the opening roller. The teeth of a support element can engage thereby into the fittings channels present between the fitting elements. The use of the support element as a combing element requires parallel rows of teeth on the circumference of the opening roller, like those shown in FIG. 8 of German Patent Publication DE 31 27 415 A1. However, parallel rows of teeth are not suitable for an effective combing out of the sliver. For this reason the device has not been accepted in the last two decades.